1. Field of the Invention
The present invention relates to inflation systems for airbags used in vehicle occupant restraint systems, particularly truck occupant protection airbags deployed as a result of rollover of the vehicle.
2. Description of the Prior Art
Airbag inflators commonly employ combustible precursors which, upon combination and reaction, either generate a gas (pyrotechnic devices) to inflate an airbag, or they generate heat used to expand a compressed gas and thereby inflate the airbag. Since the inflation gas is delivered to the airbag under pressure and at a highly elevated temperature relative to ambient conditions, the delivered gas loses heat and declines in temperature rapidly as it expands to fill the airbag. With cooling the inflation gas loses substantial pressure, with the consequence that the volume of airbag which can be inflated is restricted. Chemical inflators must typically be matched to the airbag they are intended to inflate, with each increase in size of bag requiring a larger inflator.
Due the restricted volume of space available on automobiles, and the need to have inflators which operate quickly in cases of collisions, chemical inflators have been favored for automobiles. Due to the great size of the automobile market, the manufacture of chemical airbag inflators enjoys substantial economies of scale, resulting in widespread acceptance of the devices in other applications, such as occupant restraint systems for trucks.
Trucks, however, have resources not generally available on automobiles. These resources include compressed air to operate the trafler brake lines and, in some cases, an air spring suspension. The air system supporting these devices includes air pumps and tanks of substantial volume for holding compressed air for the various vehicle systems.
It is an object of the invention to provide a system for inflating airbags, particularly on trucks, which are sized and positioned to protect truck occupants in case of rollover of the truck.
It is another object of the invention to provide a system for inflating airbags which is readily applicable to different sizes of airbags.
It is still another object of the invention to employ existing truck resources to support airbag inflation during rollover incidents.
According to the invention there is provided an airbag inflation system includes an air tank for compressed air, preferably a tank already used to support the operation of the truck brake system or suspension system. An outlet from the tank is provided, sealed with a frangible seal. A squib, is positioned with respect to the outlet to open the frangible seal upon actuation. Alternatively to a squib, an electrically actuable valve may be used. An air line connects the outlet to an airbag for inflation of the airbag from the tank. The tank is pressurized by a pump installed on the truck. Air tanks may be used in rollover events because rollover events are slow compared to transmission of the crash pulse during collision events. An advantage of the system is that their is little inflation gas cooling since the tank stores air at ambient temperatures. Larger airbags than are readily supported by chemically based inflators may be used.
Additional effects, features and advantages will be apparent in the written description that follows.